Separators are used in diverse applications such as separating manure fiber such as bedding and undigested feed from agricultural waste streams including dairy, poultry, swine and beef, etc., fruit pulp in the food processing industry, and solids from sewage.
Generally, separators are housed within a metal housing that prevents the influent, fiber, or separated liquid from spilling into the building in which the separator is housed. Generally, a separator is comprised of two compartments or stages, enclosed within a metal housing. These two compartments or stages are different interior sections of the housing. Influent, which comprises a manure slurry having solid and liquid components, is pumped into the separator from a lagoon or reception pit and flows into a first stage. Excess influent is returned to the lagoon or reception pit from a weir box overflow opening or an opening in the side of the enclosure that serves as a side wall of the first stage.
The first stage brushes on the prior art separator pass over the first stage screen at an angle perpendicular to the tangent of the screen's curve. In other words, the brushes pass over the screen at approximately a 90 degree angle over the entire semi-circle of the first stage screen. As the brush assembly rotates, passing from the vertical brushing position to the near-horizontal position at the discharge edge of the screen, the brush acts like a shovel, scooping much of the solid material up and over where it falls off from the overhead position back onto the stage one screen instead of brushing it into stage two. This leaves additional solid material in the stage one compartment reducing the efficiency of the screen.
The rollers on the prior art separator are mounted directly to rotary arms. The axle passes through the roller, through sealed metal bearings at both ends of the roller. The axle then passes through a rubber filled steel bushing that is rigidly clamped near the end of the rotary arm so that the roller follows the arm. The only resiliency to this roller apparatus is the thin rubber-like coating on the roller and the very limited flexibility permitted by the rubber filled bushing. As a result of this inflexibility, the roller cannot tolerate a foreign object without causing great stress or damage to the screen.
The rollers on the prior art separator are constructed of carbon steel with a rubber or rubber-like coating. Standard steel mechanical bearings with seals are pressed into ends of the roller cylinder and a carbon steel axle passes through sealed bearings. These bearings have limited durability and are extremely difficult to replace, as all the materials of construction are ferrous and subject to extreme corrosion when exposed to certain corrosive liquids such as animal manure. This typically necessitates replacement of the entire roller assembly including bearings and seals at great expense.
The rollers in the second stage of the prior art separator have pressed-in-place metal bearings and seals. A roller axle passes through these bearings and is clamped in a rubber-filled bushing. The seals wear out with great frequency exposing the metal bearings to the corrosive liquid being separated which quickly ruins the metal bearings. The rubber-filled bushings also have a limited life. Replacement of any of these individual components is very difficult because of corrosion, which usually necessitates the replacement of all of these components simultaneously at great inconvenience and expense.
The main rotary bearings on the prior art separator are metal bearings that must slide over the end of the shaft. Such bearings are constructed largely of ferrous material and require frequent lubrication. Typically, two styles are used, flange bearings and pillow block bearings. Both styles of bearings corrode quickly in corrosive environments such as manure liquids and aerosols and are difficult and expensive to replace. It is often impossible to remove the bearings from the end of the shaft, which typically necessitates removal of other drive components.
The prior art separator has a welded-in-place or bolted-in-place superstructure that covers the functional components of the machine, i.e., the rotary brush arms and the roller rotary press arms. The superstructure is fitted with access doors or panels to provide a way to service, adjust or observe the functional components. Even with all of the access ports open, actual access is restricted and visibility is impaired due to low light penetration. Removal of rollers, brushes and other functional components is extremely difficult because of the superstructure that remains in place even after the access panels/doors are removed.
The prior art separator has no provision for heating to prevent freezing of liquid influent inside the separator and assure continuous operation during cold weather except to cease operation accordingly or place the separator in a heated building. However, simply placing the separator in a heated building may be insufficient to avoid freezing of the liquid influent. Often cold air enters the separator from below the discharge area, freezing influent surrounding the rotary arms, thereby, preventing the rotary arms from rotating, which damages the drive components upon start-up of the separator.
The prior art separator is fitted only with hooking points for convenience in lifting the machine from above. Rigging or lifting the separator from below risks damage to fittings, sump and other vital components.
The prior art separator is fitted with first and second stage screens constructed of off-the-shelf perforated metal, usually stainless steel. Perforated metal screens must be of sufficient gauge thickness to withstand forces encountered during operation of the separator. Additionally, smaller pore sizes are desired to improve solids filtration efficiency at reasonably high flow-through rates. However, screens having these smaller pore sizes also have reduced thickness (gauge) which sacrifice durability. Perforated metal screens that are simultaneously durable, have small pore sizes for high filtration efficiency and a large percentage of open area for high liquid flow-rates are not readily commercially available.
The prior art separator has a number of shortcomings, one of which is the inefficient separation of liquids and solids. In addition, the bearings that support the axles tend to rust and wear out rapidly because of the corrosive nature of the manure slurry that is constantly being fed through the machine. The prior art separators do not work well in unheated buildings during the cold months of the year and are difficult to access for cleaning. The loading and installation of the separators is also extremely difficult as they are large and bulky. The prior art separator is constructed of ferrous material and galvanized ferrous material subject to corrosion and the corrosive manure environment.
What is needed is a separator that is more efficient, able to be easily and reliably heated, and has components that are more durable and more easily replaceable.